1. Field of the Invention
The present invention relates to an energy absorbing apparatus for a steering wheel employed in a vehicle. More particularly, the present invention pertains to an energy absorbing apparatus capable of absorbing the impact load and kinetic energy transmitted to the steering wheel in an emergency situation of the vehicle.
2. Description of the Related Art
For the purpose of reducing the impact load which acts on the steering wheel of a vehicle in an emergency situation, apparatuses in which an energy absorbing member is mounted on the steering wheel have already been proposed (e.g., Japanese Patent Publication No. 12688/1979 and Japanese Utility Model Publication No. 42231/1983).
These proposed conventional energy absorbing apparatuses, however, suffer from various disadvantages. For example, one type of conventional energy absorbing apparatus has a structure in which a multiplicity of parts are required, and another type involves a troublesome and complicated machining or working operation because of the provision of a bent portion at an intermediate position in a cylindrical member which is disposed between a steering shaft and a steering wheel rim.
In a case where a plate material is employed as an energy absorbing member in such an energy absorbing apparatus, it is particularly necessary to provide this member with a predetermined rigidity for reliably withstanding both the steering force applied thereto during steering operation and the load which the driver applies in the axial direction of the steering shaft. For this reason, the plate material employed needs to have a relatively large thickness, though on the other hand a thick-walled plate material leads to difficulty in reducing the weight of the energy absorbing member and necessitates a continuance or means for controlling the absorption of the impact load which is applied at the time of collision of the vehicle.